Allow specifying a single plugin as the plugin folder
Identify plugin folders by checking whether they contain a package.json, rather than requiring the folder to be named <name>.generate
Change how we determine if a folder is a plugin, and move
recursive loading into app (since it's really a function pertaining
to how command line parsing works)
Merge pull request #76 from adobe-photoshop/dk/load-single-plugin

Allow specifying a single plugin as the plugin folder